Vapor pocket reactor

ABSTRACT

A condensation reaction process and reactor for converting a plurality of reactants to at least one reaction product having a vapor pressure less than the vapor pressure of the reactants. The process includes heating a liquid phase of the reactants to at least partial vaporization thus forming a vapor phase of the reactants. The vapor phase reactants are passed in a vapor and or condensed state through at least one catalyst bed spaced from the liquid state to form reaction product(s). The reaction product(s) is returned to the liquid phase without additional contact with catalyst.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of and a reactor forconverting at least one reactant to at least one reaction product havinga vapor pressure less than the vapor pressure of the reactant(s). Moreparticularly, the present invention relates to a method of and a reactorfor improving conversion in equilibrium limited reactions, and forimproving selectivities in condensation reactions.

2. Description of the Prior Art

It is known to use catalytic distillation processes for oligomerizationand etherification of C₄ and C₅ iso-olefins. The process consists ofconcurrent reaction and distillation in a combinationreactor-distillation column. A catalytic distillation process isdisclosed in U.S. Pat. Nos. 4,215,011 and 4,232,177.

It is also known to prepare tertiary alkyl ethers, particularly methyltertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) byreacting an iso-olefin, typically in a hydrocarbon fraction, with analcohol, such as methanol, in the presence of an acid catalyst, forexample sulfuric acid, hydrofluoric acid, aluminum chloride or boronfluoride. As disclosed in U.S. Pat. No. 4,605,787, acidic zeolitecatalysts are also useful in these processes. Other suitable catalystare carbonaceous materials containing --SO₃ H groups, for examplesulfonated coals, sulfonated phenol-formaldehyde resins, sulfonatedcoumarone-indene polymers or sulfonated polystyrene-divinylbenzeneresins.

The catalytic distillation (catstill) process provides for both reactionand distillation concurrently in the same vessel and at least in partwithin the catalyst bed in the vessel. For example, in the catstillprocess, methanol and an isobutene-containing C₄ stream are continuouslyfed to the reactor-distillation column where they are contacted in thecatalyst section of the column. The methanol preferentially reacts withisobutene, forming MTBE, which is less volatile than the C₄ componentsof the feed and the methanol. Hence the MTBE drops in the column to formthe bottoms. However, the MTBE product returns to the liquid streamflowing downwardly through successive beds of catalyst and thus issubject to further catalytic reactions. Concurrently, unreacted C₄ (e.g.n-butane, n-butenes) are more volatile than MTBE and form an overhead.Since the reaction is reversible, conversion will be limited in partbecause of MTBE product contacting catalyst. However, by removing theMTBE as a bottoms from contact with the catalyst, the reaction is forcedto completion in accordance with Le Chatelier Principle. Therefore theprocess can provide high conversion of isobutene and methanol reactants.

The catalyst in a catstill performs both a reaction and a distillationfunction. The mass-transfer characteristics of a reactive distillationunit are critical because the unit must contribute to the vapor andliquid mass transfer. In order to affect efficient separation, thecatalyst of a catstill must be in contact with the feedstock or bulkliquid phase.

Further, multi-reaction zone catstills are limited to reacting materialswith similar volatilities. Because the catstill is an open continuousflow distillation system, reactants with different volatilities separateand stratify into different regions of the distillation tower. However,the reactants must be mixed to react. Therefore such units are limitedto feeds having similar volatilities.

In addition, balancing reaction rates with distillation rates introducesfurther complexity. Operation, construction, and maintenance of acatstill unit is a challenging undertaking. The reaction rate andseparation rate must be balanced. Each time a new reaction is run, asearch .must be made for the appropriate reaction temperature andpressure, and an appropriate reflux ratio and column height to maintaingood mixing of the reagents in the reaction zone. At all times, caremust be taken to avoid column fooding.

An object of the present invention is to provide a method of and reactorfor driving equilibrium limited reactions.

Another object of the invention is to improve selectivities incondensation reactions in which the product(s) is reactive.

Yet another objective of the invention is to improve the operability bydecoupling reaction and separation.

SUMMARY OF THE INVENTION

In accordance with a broad aspect of the present invention there isprovided a reaction process for converting at least one reactant to atleast one reaction product having a vapor pressure less than the Vaporpressure of the reactant(s). The process comprises the steps of heatinga liquid phase comprising the reactant(s) to partial vaporization thusforming a vapor phase of the reactant(s), and passing the vapor phasereactant(s) in a vapor and/or condensed state through at least onecatalyst bed separated from the liquid phase to form at least onecondensed reaction product. The product(s) is returned to the liquidphase without additional contact with catalyst.

Thus, with a plurality of reactants, the vapor phase determines thecomposition of the reactants in the catalyst bed which is different thanthe composition of the liquid phase feed to the reactor.

The reactant(s) are refluxed between the liquid phase and the vaporphase until a desired concentration of the product(s) is in the liquidphase. The product(s) tends not to return to the vapor phase because ofits lower vapor pressure. In this way the products are removed fromfurther contact with catalyst and therefore from further reactions.

In accordance with another broad aspect of the present invention, thereis provided a reactor for converting at least one reactant to at leastone reaction product having a vapor pressure less than the vaporpressures of the reactant(s). The reactor comprises means for heating aliquid phase comprising the reactant(s) to partial vaporization thusforming a vapor phase of the reactant(s), and means including at leastone catalyst bed separated from the bulk liquid phase for converting thereactant(s) to the product(s). Also included are means for passing thereactant(s) in a vapor and/or condensed state through the catalyst bed,and means for returning the product(s) to the liquid phase withoutadditional contact with catalyst.

The vapor pocket reactor (VPR) of the present invention has significantadvantages over a catstill. The present invention is useful for drivingequilibrium-limited reactions and for obtaining good selectivities incondensation reactions in which the products are as reactive or are morereactive than the starting materials. Embodiments of the VPR provide arelatively simple process which does not require bulk separation ofproduct from the reactants with recycle of the reactants. The VPR thuspermits optional batch operation not available in the prior art.

The invention contemplates a batch embodiment, and an advantage of thebatch embodiment is that reactants even of widely different volatilitiesremain in the reaction zone. Thus, the VPR can make good use of thegreater volatility of propylene vs. water for IPA and DIPE synthesis.

Examples of reactants having widely different volatilities are propyleneplus water to form isopropyl alcohol (IPA) and di-isopropyl (DIPE), andpropylene plus benzene to form cumene also have large volatilitydifferences. In these reactions propylene boils at -42° C., water at100° C. and benzene at 80° C. In prior art catstills, it is difficult tomix propylene and water in the catalyst bed because propylene tends torapidly exit the reactor with the raffinate and water goes to thebottoms. However, in specific aspects of the present invention there areprovided batch and continuous reactor designs which force thesereactants together on the catalyst to form the intended products.

Thus, the VPR can make good use of the greater volatility of propylenevs. water for IPA and DIPE synthesis. High conversions of propylene areobtained because the reaction zone is both enriched in propylene anddepleted in IPA and DIPE giving conversion both a Le Chatelier push, dueto increased propylene/water on the catalyst, and a pull, due to reducedIPA and DIPE/reactants on the catalyst

Another advantage of the embodiments of the present invention is thatthey improve the productivity of the catalyst system. The heavy productformed in each catalytic zone quickly leaves that zone, and as a liquidis not again exposed to the catalyst. In a batch embodiment of theinvention, reaction product falls to the bulk liquid zone; and in themulti-stage embodiments the product is captured in the liquid refluxwhich bypasses the rest of the catalytic zones. Thus, the chance ofreverse reaction occurrence is minimized and reaction equilibrium isshifted toward the product.

Therefore, the VPR drives equilibrium-limited reactions, and protectsreactive products. A number of commodity fuel components andpetrochemicals are products of equilibrium-limited reactions or couldbenefit from product protection provided by the method and reactor ofthe present invention. These include but are not limited to alkylation,MTBE, TAME, di-isopropyl ether (DIPE), propylene and butene hydration,aldehyde condensation, aldol condensation, ketone alkyl-silylation,ester synthesis from acids and olefins, and alcoholysis of dialkyldichlorosilanes.

In the VPR, the catalyst performs only one function, that of catalysis.The sole function of the catalyst is to convert the reactants defined bythe vapor phase. Mass transfer is achieved by boiling and condensing.Thus, catalyst contact with the feedstock bulk liquid and reactionproducts therein is avoided in all the embodiments, except a continuousVPR system, where fresh makeup feed contact with catalyst is minimizedby premixing such feed with large multiples of condensate. Furthermore,as in all other embodiments, reaction product(s) of the continuous VPRsystem, is quickly removed from the catalyst bed to avoid furtherreaction involving the product(s).

Further, the invention permits the use of a batch reactor. The batch VPRis simple to build and easy to operate. It is operated by loadingcatalyst and reactants, sealing, bringing to temperature, and turning oncondenser coolant. The reactions can be run over a wide range oftemperature without concern. The reactor pressure automatically adjuststo the combined vapor pressures of the reactor contents without largechanges in reaction zone composition.

In addition to condensation reactions, the process and system of thepresent invention are particularly useful for the following reactions;alkylation, e.g. olefin/aromatic and olefin/isoparaffin to make ethylbenzene and gasoline alkylate; dimerization; etherification; hydration;rearrangements which reduce vapor pressure; and isomerization, e.g.ketone to enol. The invention requires only that the reactant(s) arepartially vaporized in the reaction and that the product has a vaporpressure less than the vapor pressure of the reactant(s).

As used herein, "without additional contact with catalyst" means thatthe product(s) once in a liquid state is returned to the liquid phase,and that the returning liquid does not contact the catalyst bed. Thedefinition contemplates that a minimal amount of reaction producttypically will be revaporized and therefore will again contact thecatalyst bed. However, this minimal product contact with the bed willnot significantly affect equilibrium or reactant conversion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a batch reactor embodiment of thepresent invention with the reactants contacting the catalyst in a liquidstate;

FIG. 2 is schematic drawing of another batch reactor embodiment of theinvention with the reactants contacting the catalyst in a vapor state;

FIG. 3 is a schematic representation of a continuous reactor systemembodiment of the invention with the reactants contacting the catalystin a liquid state;

FIG. 4 is another continuous reactor system embodiment, also with thereactants contacting the catalyst in a liquid state;

FIG. 5 is a cross-sectional side view of a continuous multi-stagereactor embodiment of the invention with the reactants contacting thecatalyst in a vapor state;

FIG. 6 is an cross-sectional side view of the top bubblecap tray andcatalyst bed of the reactor of FIG. 5;

FIG. 7 is another continuous reactor system embodiment, also with thereactants contacting the catalyst bed in a vapor phase;

FIG. 8 are curves of equilibrium conversion reactions vs. temperature inthe reactor of FIG. 1 and in a laboratory autoclave;

FIG. 9 is a plot of the methanol enrichment ratio vs. weight percent ofmethanol in the reactants of FIG. 1;

FIG. 10 are plots of percent conversion vs. contact time for the reactorof FIG. 1, and of a laboratory autoclave for TAME synthesis;

FIG. 11 is a graph of product distribution from reaction of IPA to DIPEsynthesis in the FIG. 1 reactor;

FIG. 12 is a graph of product distribution from reaction of IPA to DIPEin a conventional fixed bed reactor; and

FIGS. 13 and 14 are graphs of isobutylene conversion reactions in thereactor of FIG. 1 and in a laboratory autoclave.

DESCRIPTION OF SPECIFIC EMBODIMENTS Batch VPR with Liquid Feed toCatalyst

With reference to FIG. 1, there is shown a schematic of a single stageVPR embodiment of the present invention in the form of a batch reactor10. A modified Parr autoclave is suitable as a lab embodiment of thebatch reactor 10. A catalyst bed 11 is suspended in a screened holder 12directly beneath a condenser 13 by a pair of arms 14. Alternatively, thecatalyst bed may be supported in any suitable structure which permitsfluid passage therethrough to contact the catalyst. For example, thesupport structure may be in the form of permeable plate arrays asdisclosed in U.S. Pat. No. 5,073,236, or a foraminous horizontalsupport.

Thus, the catalyst bed 11 is located in a vapor zone 15 of the reactorand not in the liquid reactant zone 16 at the bottom of the reactor asis normally done in a batch reactor. The VPR takes advantage of anability in accordance with the invention to position a heterogeneouscatalyst in the vapor zone 15, hence the name Vapor Pocket Reactor(VPR).

Another advantage of placing the catalyst in the vapor zone 15 is thatthe composition of the reactants in the catalyst bed are determined bythe composition of the vapor phase and not by the composition of theliquid phase 16. To initiate the reaction, the catalyst 11 is suspendedin the vapor zone 15 beneath the condenser 13. Then the reactor 10 issealed or closed, and coolant such as water is flowed through thecondenser 13.

A controller 17 is attached to a heating mantle 18 in which the reactor10 is positioned. The controller 17 is set to apply heat to the liquidportion 16 until the reactor 10 reaches a predetermined temperature atwhich time the reactants are partially vaporized. Also, water is fedthrough the condenser 13 such that heat is removed by the condenser 13at the rate at which the mantle 18 is supplying heat to thereby balancethe input and the output of heat. Obviously, a small amount of heat isalso lost via radiative cooling which can be minimized, with insulation.Further, heat is also supplied or removed by the reactions.

In the FIG. 1 batch embodiment, the vapor travels upwardly and aroundthe catalyst bed 11 through the space between the bed and the interiorwalls of the reactor 10. This occurs because the pressure drop acrossthe catalyst bed causes the vapor to take the path of least resistancearound the bed from the liquid source 16 of vapor at the bottom of thereactor 10 to the condenser 13 which is the sink for the vapor. Thus,reflux is generated. For every gram of condensate formed by thecondenser 13, one gram of liquid evaporates from the bulk liquid 16 atthe bottom of the reactor 10. Therefore, if a large amount of heatenergy is applied to the reactor 10, the bulk liquid at the bottom willboil forming a stream of vapor moving up around the catalyst bed 11 tothe condenser 13 where a condensate stream of reactants is formed whichtrickles downwardly through the catalyst bed 11 to be converted intoreaction product. The product then drips from the catalyst bed down tothe bulk liquid 16 at the bottom of the reactor 10.

For a given surface area condenser 13, increasing the flow rate of waterthrough the condenser 13 will increase the rate at which heat isremoved, and the increase in heat removal rate calls for more heat to beapplied. The increase in applied heat increases the rate at which theliquid is turned into vapor. This action increases the flux of thecondensate across the catalyst bed. Thus, to circulate the feed acrossthe catalyst, the liquid is heated and the vapor is cooled. This servesto reflux the system by vaporizing the liquid and condensing the vaporto provide a steady stream of condensate as fresh feed to the catalystbed.

In this embodiment, the catalyst feed is condensate. In another batchreactor to be described with reference to FIG. 2, and in continuousreactor embodiments to be described with reference to FIGS. 5 and 7, thefeed to the catalyst beds is in a vapor state. Thus, the feed to thecatalyst bed can be liquid (condensate) and/or vapor. However, animportant aspect of the invention is that the composition of thecatalyst feed is at least predominately determined by the vapor phase,and not by the liquid feed (phase) to the reactor. Therefore, the feedto the catalyst is not the feed to the reactor.

BATCH VPR WITH VAPOR FEED TO CATALYST

FIG. 2 shows another embodiment of a batch reactor where a bed ofcatalyst 20 is extended out to the wall on one side of the reactor 21,and is suspended below a bubble-cap tray 23. Heat is applied to the bulkliquid 25 as in FIG. 1 to form a vapor phase in the vapor zone 22. Thevapor rises though the catalyst bed 20 forming product(s) therein, andthrough the tray. The product(s) is condensed by heat exchange action ofa condenser 26, and falls back on the bubble-cap tray 23. Liquid on thetray 23 flows over a wier 27, down a downcomer 24 to the bulk liquid 25at the bottom of the reactor 21. The downcomer 24 extends down into thebulk liquid 25 and provides a pressure drop across the catalyst bed sothat the vapor is forced upwardly through the catalyst bed 20.

The major benefits of reactors designed in accordance with the presentinvention are twofold. First, selectivity of condensation reactions isimproved in a reaction where reactants A go to product B which can go toproduct C, and it is desired to concentrate product B. A typical exampleis olefin oligomerization where it is desired to convert a monomer to adimer. The reactors of this invention prevent the dimer from furtherreaction to higher oligomers or isomers or decomposition product,because the dimer once formed does not again come into contact withcatalyst. The dimer like other condensation products being of highermolecular weight will have a significantly reduced vapor pressure vs.the monomer. Therefore, the concentration of dimer product in the vaporphase is reduced significantly compared to that of the monomer(reactant). The first product formed has a lower vapor pressure andsubstantially all remains in the liquid phase. The higher the molecularweight of the monomer (reactants), the more dramatic the difference invapor pressure. Therefore, the product is more efficiently isolated fromthe catalyst. This action shifts the equilibrium further towards thecondensation product, as well as preventing further reaction ofcondensed material. In a selective conversion process, it is desirableto operate at or near reaction conditions for 100% conversion. Thus, theinvention provides a form of product protection because once product iscondensed into the liquid phase, the product does not return to thereaction zone.

Alkylation is an example of a reaction whose selectivity can be improvedby VPR processing. An important measure of alkylation product quality isthe trimethyl pentane:dimethylhexane (T/D) ratio. A second importantproduct quality measure is the C₉ + yield. The undesirable products areC₉ + and dimethylhexanes. Both are products which can be made bysecondary reactions of the primary product trimethylpentanes. In theVPR, the trimethylpentanes are removed upon formation, reducing theformation of dimethylhexanes and C₉ +.

The second general class of reactions benefitted by the presentinvention are equilibrium condensation reactions in which the amount ofreagents going to product is limited by thermodynamics, for example, theTAME reaction. The invention optimizes these reactions by increasing theconcentration of the reactants and decreasing the concentration of theproduct in the catalyst bed. This is achieved by the reactants in thevapor phase being enriched by the light materials and depleted of thecondensed materials. Thus, equilibrium-limited condensation reactionswill obtain higher conversion of reactants to desired product.

CONTINUOUS VPR WITH LIQUID FEED TO CATALYST

With reference to FIG. 3, there is shown a continuous VPR which isfunctionally similar to FIG. 1 embodiment. As discussed above, theessential elements of the batch VPR embodiment of FIG. 1 include acondenser 13, a catalyst bed 11, a vapor space 15 and a liquid phase 16.In the FIG. 3 embodiment, a preheater 80 functionally corresponds to thecondenser 13 of FIG. 1, and a reactor 81 also has a catalyst bed 82, avapor space 83, and a liquid phase 84.

Feed is initially charged to the reactor 81 by a line 96. When theliquid phase of reactants 84 is at a predetermined level, a valve 97 isclosed, and heat is applied to the lower end 93 of the reactor to formthe vapor phase 83. Heat may be applied by any of several known systems,such as a steam jacket or reboiler at the lower end 93 of the reactor. Abooster pump 85 is provided in a line 86 for maintaining a positivepressure on the catalyst bed 82 to prevent the vaporized reactants inthe vapor space 83 from entering the catalyst bed 82. Heat applied tothe liquid 84 produces more vapor which is forced out of the reactor 81via a line 87 to the feed preheater 80 where the vapor is fed through avapor distributor 88, such as a bubble cap tray, and condensed by thecondenser 105 or by direct heat exchange with liquid makeup feedstockfed to the preheater 80 by a line 94 and a pump 98. The condensedreactants in the feed preheater 80 are passed to the top of the catalystbed 82 by the pump 85 where the reactants trickle through the bed andform product which drips down to the liquid phase 84.

The vapor stream in the vapor pumparound line 87 is fed to the feedpreheater 80 at rate such that the weight ratio of recycle vapor toliquid makeup feed in the preheater 80 is from about 1:1 to about 100:1,preferably from about 2:1 to about 20:1. A suitable ratio is 10:1, byweight, such that the condensed vapor is dominant when the condensedvapor and feed mixture passes through the catalyst bed. Product formedin the catalyst bed 82 falls into the liquid phase to be removed by aproduct stream line 95. Thus, the system of FIG. 3 significantly reducesfurther reaction with the product to a minimal level, and also drivesequilibrium-limited reactions to the desired product. The amount of feedto the preheater 80 though line 94 and pump 98 is controlled to makeupfor product removed by line 95, and thus maintains a desired liquidlevel in the reactor 81. The fresh feed pump 98 and a product pump 100work together to maintain an overall throughput. The pump 99 sets theoverall reactor system hydrocarbon inventory. The reboiler 93 and thebooster pump 85 work together to control reflux by maintaining a desiredliquid level in the preheater 80.

Heat 93 applied to the liquid phase 84 of the reactor 81 controls therecycle weight ratio of vapor pumped around line 87 to liquid makeupfeed 94 to the preheater 80. Increasing the amount of heat applied tothe liquid will increase the amount of vapor. It should be noted that ata fixed pressure, the reactor is a constant temperature device. All heatapplied to the reactor 81 is transferred into vaporization and increasesrecycle ratio.

As in the batch VPR embodiments, reactor temperature and pressure arelinked in the continuous VPR. In order to change the temperature of thereactor, the pressure of the reactor must be changed. Changingtemperature requires a change in pressure. Thus, without a pressurechange, if more or less heat is applied to the liquid phase in thereactor, reflux by vaporization and condensation will increase ordecrease without changing the temperature in the reactor.

In operation, the liquid phase is initially filled to a predeterminedlevel, and the liquid level controller maintains the predetermined levelby controlling the makeup feed and/or the rate of product removal fromthe reactor. For example, if the rate of feed is reduced, the liquidlevel controller will automatically slow the rate of product withdrawalto maintain the predetermined level. It should be noted that, with otherconditions constant, the slower the rate of feed and product withdrawal,the higher the reflux ratio and the closer operation will be toequilibrium or complete reactant conversion.

In a TAME catalytic distillation reaction in a catstill, a C₅ feedstockcontaining C₅ paraffins, C₅ linear olefins and reactive isoamylenes isconverted into TAME as a bottoms product. C₅ paraffins and unreactive C₅linear olefins and unconverted isoamylenes and methanol exit as anoverhead or TAME raffinate. Generally, all the TAME raffinate and TAMEproduct are blended back together in the gasoline pool, with TAMEproviding octane enhancement. In comparison, the VPR embodiment of FIG.3 simply takes the typical C₅ feedstock and processes it to provide asingle TAME product stream 95 for the gasoline pool without the need forrecombining reactor-separated streams. However, depending upon reactionconditions, methanol may be separated from the product stream 95 forrecycle to the system.

With reference to FIG. 4, there is shown a continuous reactor systemembodiment wherein the reactant(s) contact the catalyst bed 128 in aliquid phase. A liquid feedstock of reactants is passed by a line 120through a nozzle 122 to the top of a reactor 123. The reactor has a tray124 with a wier 126 at one side thereof. The cold feed and spray fromthe nozzle acts as a condenser. If additional condensation is desired,for example to increase recycle ratio, a typical heat exchangercondenser 126 can be used. The tray 124 has an opening 130 with abooster pump 132 therein. A liquid level controller 134 monitors thelevel of liquid in the tray 124 and prevents spill over the wier 126 bycontrolling the pump 132. Heat is applied to the reactor 124 asdescribed with reference to FIG. 3. The pump 132 maintains a positivepressure on the top of the catalyst bed 128. Reactants are partiallyvaporized from the liquid phase 140, and pass upwardly through theopening 142 defined by the side of the bed 128 and the wier 126. Thevapor phase mixes with the fresh feed spray from the nozzle, condenses,and falls into the tray 124. From the tray 124 reactants pass throughthe opening into the catalyst bed. Product formed in the bed falls intothe liquid phase 140, and is removed by a line 142.

CONTINUOUS VPR WITH VAPOR FEED TO CATALYST

With reference to FIG. 5, there is shown a multistage embodiment of aVPR 29 which will accommodate continuous flow to produce large volumesof product. A catalyst bed 30-32 is suspended in the vapor space 38-40below each of three liquid filled trays 36-38. A downward flowing liquidpath is provided between the trays 36-38 by downcomers 33-35, with eachdowncomer being fed by condensate overflowing a weir 41-43 on each tray.Each tray 36-38 has a "bubble cap" structure as shown in FIG. 6 whichcomprises a plurality of holes with a cylindrical member 55 about eachhole and extending upwardly. Liquid on each tray exits the tray 36 viathe weir 41. Each cylindrical member has a cap 56 spaced from the topend thereof. The cap 56 has a skirt 57 portion extending downwardlyabout the top end of the cylindrical member 55 but spaced therefrom suchthat vapor passing upwardly through the member is deflected down by thecap 56 and into the liquid 58 on the tray.

The caps 56 prevent the liquid 58 in the tray 36 from flowing down thecylindrical tubes 55 while vapor is rising from the catalyst bed 30 upthrough the tubes. The caps 56 function to deflect the vapor downwardlyin the liquid 58 and bubble therethrough. Hence, the term "bubblecap".Preferably the top of the caps 56 are above the level of the top of thewier 41, and the skirt 57 of each cap extends downwardly into the liquid58 on the tray 36. Also, the top of each cylindrical tube 55 ispreferably at a height slightly above the height of the weir such thatthe possibility of liquid passing down the cylindrical tubes is furtherminimized.

The initial direction of travel of the product(s) formed in the catalystbeds is not clear. One possibility is that the product is displaced fromthe catalyst bed by upwardly flowing vapor which strips each catalystbed and carries reactants and product into the liquid layer on the traydirectly above. The vapor is intimately mixed with the liquid in eachtray 36-38, such that the liquid acts as a heat exchanger to remove heatfrom the vapor and to selectively condense reaction product out from thevapor stream and into the liquid. This selective condensation occursbecause the reaction product has a lower vapor pressure than that of thereactants.

Another possibility is that the product made in each catalyst bed fallsinto the tray below, with the unconverted vapor being contacted with theliquid on the tray above where heat and mass transfers occur. Acombination of part of the product being displaced upwardly into thetray above and part of the product falling into the tray below may alsohappen. However, experiments have not yet clarified whether the productis swept up to the tray above each catalyst bed, falls to the tray belowor a combination of both. In any case, the important aspect of theinitial direction of the product is that upon exiting a catalyst bed theproduct enters the downward flowing path as defined by the trays 36-38,weirs 41-43 and downcomers 33-35, and does not again come into contactwith catalyst.

Liquid feed is fed to the reactor 29 by a line 50 with branches 51-53feeding the various vapor spaces where reactants are vaporized from theliquid stream defined by the liquid filled trays 36-39, the downcomers33-35 to the bottoms liquid product zone. Vapor passing upwardly throughthe catalyst beds 30-32 flows upwardly through the cylindrical members55 on the respective tray 36-38 above each catalyst bed 31-32 andprevents downward flow of liquid from the trays. With catalyst beds30-32 beneath the trays, the catalyst beds are continuously contacted bythe upflowing reactants in a vapor phase. The rising vapor is enrichedin the reactants, e.g. methanol and iso-olefin that were depleted in thecatalyst bed directly below. Unreacted vapor exits the reactor by anoverhead line 61.

The vertical temperature profile of the reactor is monitored by aplurality of temperature sensors and the feed rate and/or heat rateapplied to the reactor are controlled accordingly. Heat may be appliedto the reactor by any of several known systems, such as a steam jacketor reboiler at the lower end 93 of the reactor.

Although this embodiment is described with a bubble cap tray,alternative trays may be used provided they function as a one-way valvepermitting upward flow of vapor and preventing downward flow of theliquid on the tray. Other examples are flapper trays and sieve trays.

The reaction in the reactor 29 is not believed to be a gas phasereaction. The vapor phase is at its dew point, and contact with a highsurface area catalyst should cause capillary condensation to occur.Thus, even though it is in the vapor space and contacted by vapor, thecatalyst can be wetted at all time with liquid condensate. The heat ofreaction is removed by the upflowing vapor and is used to help run thedistillation. As with the other embodiments of the invention, anadvantage of the multistage VPR is that product formed at any catalystbed is removed from the reactor without any additional catalyst contact.This is very important because of the reversible nature ofequilibrium-limited reactions and to prevent the product from enteringfurther forward secondary reactions. Anytime product enters a reactionzone, it has the potential to undergo the highly undesired decompositionreaction to starting materials. This is prevented in the VPR by the lowvolatility of the product. Once in the liquid phase on any tray, productwill flow to the bottom 60 of the VPR via the flow path defined by thetrays 36-38, weirs 41-43 and downcomers 33-35 without contactingcatalyst. Product is continuously removed from the reactor 28 by a line62. In comparison, typical known catstill operation inevitably leads tomore product reaction as heavy product becomes more concentrated becausethe condensed product is brought back into contact with the catalystbeds. Furthermore, the reaction temperature also rises in successivelylower reaction zones which additionally increases undesirable productreactions.

Depending on the reaction and the catalyst, it should be noted that avery slight fraction of the liquid from the tray below or from the trayabove may become entrained in a catalytic zone. However, even in thiscase essentially all the liquid in the multistage reactor bypasses thecatalytic zones.

The benefits of the continuous multi-stage flow VPR shown in FIG. 5 aresimilar to those of the batch VPR of FIG. 1. For example, thecomposition of the reactants in each catalyst bed is determined by thecomposition of the vaporized bulk liquid supplied to the reactor.

The FIG. 5 multi-stage VPR unit is also functionally similar to thebatch VPR of FIG. 1 in that pumping of the reactants across the bed isaccomplished by reflux, i.e., by cyclic vaporization (boiling) andcondensing. In the batch VPR of FIG. 1, the ratio of the weight percentof the feed stock in the liquid phase and in the vapor phase isconstant. The composition of the liquid phase changes with time, but therelative amounts of liquid and vapor remain the same. For every gram ofliquid that is vaporized there is condensation of a corresponding amountof vapor from the condenser to be returned to the liquid phase. This isreflux and is similar or analogous to moving a stream using a pump.

In an alternative embodiment of FIG. 7, the catalyst bed 82 of FIG. 3 ismoved to the vapor pump-around line 87. In this case, reactants arepassed through the catalyst bed in a vapor state. Thus, the system ofthis embodiment functions in a manner similar to that of FIG. 2.

Etherification to make fuel ethers is an important reaction to becarried out in accordance with the VPR systems of present invention.Another important reaction is esterification. Etherification is used tomake MTBE, TAME and ethers from the mixed iso-olefins in FCC gasoline.As noted above, the VPR systems of the present invention are suitablefor other condensation reactions such as isoparaffin olefin alkylation,the formation of esters for synthetic lubricants and additives such asamides, and oligomerization of olefins, for example isobutylenedimerization. The isobutylene dimer is used as an aromatic alkylate. Thesystems are also useful in the addition of hydrogen sulfide to olefinsmake thiols and thioethers, and for hydration reactions such as theaddition of water to olefins to make alcohols.

A common element of all of the embodiments of FIGS. 1 though 7 is thatthe invention improves the productivity of the catalyst systems becausethe catalyst bed(s) is enriched in more volatile reactants, and depletedof products which are rapidly removed from the catalyst, thus shiftingthe reaction equilibrium towards the desired condensed products.

EXAMPLES

Table I shows results of C₅ /C₆ FCC gasoline etherification atequilibrium in the batch VPR of FIG. 1, and compares the results withunmodified, liquid phase autoclave processing wherein the top of theautoclave is open to atmospheric pressure. The feed was 50 g of C₅ /C₆FCC gasoline (0.17 moles of etherifiable olefins), 5.55 g of methanol(0.17 moles). The reaction temperature was 190° F. for the batch VPR runand 185° F. for the autoclave run. It should be noted that lowertemperature favors MeOH and olefin conversion to ether. 1.5 g ofAmberlyst-15 was used as catalyst, and the run time in each case wastwenty hours which was sufficient to bring the reactor to equilibrium.

                  TABLE I                                                         ______________________________________                                        Etherification                                                                               Autoclave Run                                                                          VPR Run                                               ______________________________________                                        % C5 Conversion  51         80                                                % C6 Conversion  28         60                                                % MeOH Conversion                                                                              35         70                                                Wt % Ethers      10         20                                                ______________________________________                                    

The VPR run outperformed the standard autoclave processing, withmethanol and olefin conversion being doubled. The product from theautoclave was 6 wt % methanol, while the product from the VPR was only 3wt % methanol.

By adjusting the methanol to olefin ratio, the batch VPR of FIG. 1provides a breakthrough in C₅ + etherification, and substantiallyimproves the yields and resultant economics of C₅ and C₆ olefinetherification. The process of the present invention obtains very highconversions of C₅ + iso-olefin. Thus, operation in accordance with thepresent invention leads to at least a reduction in the size of amethanol recovery unit for removing methanol from the overhead stream ofthe typical catstill for recycle to the catstill. Optimization of theVPR has the potential to eliminate the need for such a unit.

Further, use of the VPR can eliminate the need for a hydrotreater topretreat the feed. A typical feed may have about 1% 1,3-butadiene whichtends to significantly coke catalyst. In a known process for reacting1,3-butadiene and isobutylene with methanol using acid catalysis,isobutylene is more reactive than 1,3-butadiene. The process selectivelyreacts isobutylene to MTBE in the presence of an excess of 1,3-butadieneby operating at high methanol to olefin ratio, e.g., 5:4.However,refinery operators prefer not to operate at high methanol to olefinratio because such operation would require a relatively large methanolseparator and methanol recycle. Therefore, operators prefer to performselective diene hydrogenation in a hydrotreater to reduce 1,3-butadieneto butene.

The VPR permits the use of a reactant feed stream to the reactor havinga methanol to olefin weight ratio as low as 1:1. However, internally thevapor and/or condensate phases would contact the catalyst bed(s) at ashigh as a 3-4:1 methanol:olefin mole ratio. This methanol enrichment atthe catalyst zone prevents or at least minimizes the potential of cokingthe catalyst by diene oligomerization. Thus, the VPR would be able toprocess the 1,3-butadiene and isobutylene reaction without the need fora hydrotreater to perform the hydrogenation step.

The VPR shifts the apparent equilibrium of equilibrium-limited reactionsin which the boiling point of the product is higher than the boilingpoint of the reactants. A specific case is the formation of TAME fromthe reaction of isoamylene with methanol.

FIG. 8 shows a plot of equilibrium isoamylene conversion vs. temperaturein each of the batch VPR of FIG. 1 and the laboratory autoclave at amethanol:isoamylene feed weight ratio of 1.25. The FIG. 8 plotsdemonstrate that the VPR of FIG. 1 approximately doubles equilibriumconversion of isoamylene to TAME over the temperature range of 170° F.to 225° F.

The catalyst brings the surrounding reaction mixture to equilibrium. Thereason TAME production is doubled in the VPR compared to a regularautoclave is that the surrounding reaction mixture in the VPR ismethanol rich and TAME poor. This is because in the VPR the reactionmixture surrounding the Amberlyst-15 is condensed vapor, which has avery different composition from the bulk reaction mixture that surroundsAmberlyst-15 in the standard autoclave runs. This is demonstrated by thedata in the following Tables 2 and 3.

In the following examples, methanol (Baker), isoamylene (Aldrich),hexane (Aldrich), and Amberlyst-15 (Rohm and Haas) were used withoutfurther purification. Amberlyst-15 was refluxed in 3 gm of methanol pergm of catalyst for 1 hour and then filtered and dried overnight at 120°C. A 25 wt % isoamylene, 25 wt % n-pentane, 14 wt % methanol, and 37 wt% n-hexane feedstock was formulated. The paraffins were included asunreactive internal standards. This near stoichiometric ratio (1.25moles methanol per mole isoamylene) was chosen because of its commercialrelevance. 0.25 gm of Amberlyst-15 was used to convert 81.5 gm feedstockin a side-by-side comparison of the VPR of FIG. 1 (Amberlyst-15 in thevapor space) with a regular autoclave (Amberlyst-15 in the liquid). Theexperiments were run until the composition by GC remained constant,indicating that equilibrium had been reached.

Four blends were prepared and examined to determine the differences incomposition between the solution and vapor phases in the VPR which arelisted in Table 2. Each blend (250 gm) was placed into a 600 ml VPRwithout catalyst and brought to 230° F. The liquid and vapor weresampled alternately and analyzed by GC to determine compositions shownin Table 3. Table 4 provides ratios of concentrations in Tables 2 and 3.The last two columns in Table 4 provide the relative enrichment ofmethanol vs isoamylene in the reaction zone and the relative depletionof TAME vs. isoamylene in the reaction zone, respectively.

                  TABLE 2                                                         ______________________________________                                        Liquid Phase Compositions                                                     Blend MeOH     Isoamylene                                                                              TAME  Pentane                                                                             Hexane                                                                              Total                              ______________________________________                                        A     12.5     24.3      0.0   24.7  38.5  100.0                              B     8.6      22.4      0.0   21.1  47.9  100.0                              C     4.8      13.4      24.8  13.2  43.8  100.0                              D     1.6      13.6      26.2  13.6  45.1  100.0                              ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Vapor Phase Compositions                                                      Blend MeOH     Isoamylene                                                                              TAME  Pentane                                                                             Hexane                                                                              Total                              ______________________________________                                        A     19.8     29.3      0.0   33.1  17.8  100.0                              B     23.2     26.5      0.0   28.3  22.0  160.0                              C     22.6     23.0      5.2   26.8  22.4  100.0                              D     14.8     26.5      6.0   29.6  23.1  100.0                              ______________________________________                                    

                                      TABLE 4                                     __________________________________________________________________________    Ratios                                                                            MeOH Vapor                                                                           TAME Vapor                                                                            Isoamylene V                                                                          M/A-V.sup.a                                                                        T/A-V.sup.b                                   Blend                                                                             MeOH Liquid                                                                          TAME Liquid                                                                           Isoamylene L                                                                          M/A-l                                                                              T/A-L                                         __________________________________________________________________________    A   1.6    --      1.2     1.4  --                                            B   2.7    --      1.2     2.3  --                                            C   4.7    0.21    1.7     2.7  0.16                                          D   9.2    0.23    2.0     5.0  0.16                                          __________________________________________________________________________     .sup.a Methanol to isoamylenes mole ratio in the vapor phase divided by       the same ratio in the liquid phase.                                           .sup.b TAME to isoamylenes mole ratio in the vapor phase divided by the       same ratio in the liquid phase.                                          

FIG. 9 is a plot of the methanol enrichment ratio (wt % MeOH in vapor/wt% MeOH in liquid) vs. wt % methanol in the liquid phase, anddemonstrates a dependence of methanol enrichment upon methanolconcentration. The reason for this dependence is the highly nonidealcharacter of methanol/hydrocarbon solutions. Unlike TAME/hydrocarbonsolutions, the vapor composition above nonideal methanol/hydrocarbonsolutions cannot be predicted using Raoult's Law. Less methanol insolution means less hydrogen bonding, and higher relative methanol vaporpressure. This exactly what is needed to drive the reaction equilibriumtowards TAME. As TAME is formed, the methanol concentration in the bulkliquid drops, and the vapor phase enrichment ratio rises.

With the data in Tables 2-4 and FIG. 9, the composition of the catalystzone in a VPR TAME reaction can be calculated from the composition ofthe bulk reaction mixture. As stated above, the condensate is enrichedin methanol and depleted in TAME relative to the bulk liquid whichshifts equilibrium conversion in favor of TAME production. As shown inFIG. 10, at equilibrium at 170° F. the VPR achieves 92 wt % isoamyleneconversion vs. 58 wt % for the autoclave. The VPR does not stop at 58%isoamylene conversion because when both reactors have reached thatpoint, the methanol:isoamylene:TAME mole ratio surrounding the catalystin the autoclave is ca. 3:2:2 while in the VPR the same ratio calculatedfrom the data in Tables 2-4 is ca. 30:8:1. At equilibrium in the VPR,the mole ratio changes to ca. 6:1:2. TAME becomes an important componentof the equilibrium condensate in the VPR because the reactants havenearly completely converted.

The kinetics of the VPR of FIG. 1 and of a typical autoclave wereinvestigated at 170° F., a typical temperature for commercial TAMEsynthesis. The graphs of FIG. 10 show that both the VPR and theautoclave reach respective equilibriums after identical contact times,the x-axis being space time. The horizontal lines at about 62% and about92% conversion are the equilibrium conversion for the autoclave (A/C)and the VPR reactions, respectively. The VPR has a kinetic advantagebecause the continuous removal of TAME from the reaction zone reducesreverse reaction. Thus, FIG. 10 demonstrates the increase inproductivity of the batch VPR embodiment of FIG. 1 over a typicallaboratory autoclave. This increase in productivity is unexpectedbecause of the lower concentration of moles of reactants in the vaporrelative to the liquid.

As discussed above, product protection is another general advantage ofthe VPR. In many chemical reactions in known catstills, selectivity atlow conversion is excellent, but at higher conversions selectivity dropsdue to secondary reactions of the desired kinetic products. In the VPR,higher boiling products are effectively removed from the reaction zoneupon their formation. Due to their higher boiling points, the productsremain in the bulk solution where no secondary reactions can occurbecause the bulk solution does not contact the catalyst. The reactionzone is enriched in reagents and depleted in products.

IPA Conversion to DIPE

Amberlyst-15 was treated overnight in a soxhlet extractor with refluxingmethanol. It was then dried at 212° F. overnight and stored for usewithout further treatment. A commercial acidic catalyst in an extrudatecomprising 70 wt % Beta and 30 wt % ZrO₂ binder (Zirconia) zeolite wasused with no pretreatment.

A 450 cc VPR was loaded with 150 gms IPA and 5 gms of the above treatedAmberlyst-15. An identical experiment was run substituting 5 gms of theBeta catalyst for the Amberlyst-15.In each case, the VPR was sealed andbriefly evacuated using house vacuum. The VPR was then heated to 300°F., and compressed air was blown rapidly though the condenser. Theseconditions were maintained for 48 hrs. Prior experiments showed thatbeyond 48 hrs, increasing contact time did not change the productcomposition as determined by GC. Thus, 48 hrs is sufficient to bring thereaction to equilibrium. The VPR was then cooled and the reactorcontents analyzed yielding the product distribution shown in FIG. 11. Asexpected, the same product distribution was obtained with both catalystsindicating that these conditions achieved equilibrium.

Fixed bed equilibrium results were obtained as follows. A 12 inchlength, 0.5 inch diameter reactor was loaded with 10 gms of the abovetreated Amberlyst-15 catalyst. It was sealed and pressure tested. IPAwas delivered to the reactor with a Milton Roy pump at varying ratesuntil the composition of the product stopped changing with changes inrate (at 5 gm/hr). The total product stream was passed though acondenser held at 10° F. The gas stream passed through a backmixer, asample bomb, and a gas meter. The product distribution is shown in FIG.12. Thus, the VPR shifts equilibrium producing a higher yield of desiredDIPE product.

Isobutylene Dimerizations

A 450 cc VPR was evacuated and then loaded with 90 gms isobutylene and 5gms of the above described Beta catalyst. The reactor was heated to 140°F. and held there for 4 hours while a slow steady stream of tap waterwas flowed through the condenser. Then the reactor was cooled to roomtemperature. The entire contents of the reactor were transferred to ahoke vessel. This was sampled with a high pressure syringe and analyzedby GC. The products were characterized only as dimers and oligomers.There were only two dimers formed, 2,4,4-trimethyl-1-pentene and2,4,4-trimethyl-2-pentene. This experiment was repeated except thereactor was held at 140° F. for 8, 12, and 16 hours. The productcomposition and dimer selectivity are shown in FIGS. 13 and 14 on theVPR lines.

The above experiments were then repeated at 4,12 and 16 hours in astandard laboratory autoclave where the catalyst is stirred in theliquid phase. The product composition and dimer selectivity is given inFIG. 13 and 14 on the autoclave lines. The VPR improved the selectivityof this reaction by preventing secondary reaction of the kinetic product2,4,4-trimethyl -1-pentene. Both reactions with isobutylene (monomer) toform oligomer and isomerization to form 2,4,4-trimethyl -2-pentene areprevented.

CATALYSTS

Catalyst useful for MTBE and TAME processes in the VPR are any one ofsolid acid catalysts, such as sulphonated polystyrene resins (H₂ S0₄fixed on polymer) or zeolites. Other suitable catalyst are noted abovein the description of the prior art. Obviously, the catalyst used in aspecific process is determined by the reaction process contemplated. Onewould first identify the process and then use whatever catalyst isneeded for that particular process.

Catalyst suitable for the MTBE or TAME processes are cation exchangeresins which contain sulfonic acid groups, and which have been obtainedby polymerization or copolymerization of aromatic vinyl compoundsfollowed by sulfonation. Examples of aromatic vinyl compounds suitablefor preparing polymers or copolymers are styrene, vinyl toluene, vinylnaphthalene, vinyl ethylbenzene, methyl styrene, vinyl chlorobenzene andvinyl xylene. There are a large number of methods used for preparingthese polymers. For example, polymerization alone or in admixture withother monovinyl compounds, or by crosslinking with polyvinyl compoundssuch as divinyl benzene, divinyl toluene, divinylphenyl ether andothers. The polymers may be prepared in the presence of absence ofsolvents or dispersing agents. Also, various polymerization initiatorsmay be used, e.g., inorganic or organic peroxides, persulfates, and thelike.

The sulfonic acid group may be introduced into these vinyl aromaticpolymers by various known methods, such as, by sulfating the polymerswith concentrated sulfuric acid or chlorosulfonic acid, or bycopolymerizing aromatic compounds which contain sulfonic acid groups(see e.g., U.S. Pat. No. 2,366,007). Further sulfonic acid groups may beintroduced into these polymers which already contain sulfonic acidgroups, for example, by treatment with fuming sulfuric acid, i.e.,sulfuric acid which contains sulfur trioxide. The treatment with fumingsulfuric acid is preferably carried out at 0° C. to 150° C. and thesulfuric acid should contain sufficient sulfur trioxide after thereaction. The resulting products preferably contain an average of 1.3 to1.8 sulfonic acid groups per aromatic nucleus. Particularly, suitablepolymers which contain sulfonic acid groups are copolymers of aromaticmonovinyl compounds with aromatic polyvinyl compounds, particularly,divinyl compounds, in which the polyvinyl benzene content is preferably1% to 20% by weight of the copolymer (see, e.g., German PatentSpecification No. 908,247).

The ion exchange resin is preferably used in a granular size of about0.25 to 1 mm, although particles from 0.15 mm up to about 1 mm may beemployed. The faster catalysts provide high surface area, but alsoresult is high pressure drops through the reactor. The macroreticularform of these catalysts is preferred because of the much larger surfacearea exposed and the limited swelling which all of these resins undergoin a nonaqueous hydrocarbon medium.

Similarly, other acid resins are suitable, such as perfluorosulfonicacid resins which are copolymers of sulfonyl fluorvinyl ethyl andfluorocarbon and described in greater detail in DuPont "Innovation",Volume 4, No. 3. Spring 1973 or the modified forms thereof as describedin U.S. Pat. Nos. 3,784,399, 3,770,567and 3,849,243. Cation exchangeresin structures prepared by the process described in U.S. Pat. No.4,250,052, may also be employed.

Other suitable catalysts are H₃ PO₄ on Kieselguhr, AlCl₃, ZrO₂ -H₂ S0₄,BF₃ -Si0₂, AlCl₂ /Si0₂, MgO₂ (base) and Nafion-4 (Rohm & Haas).

The acidic zeolite catalyst which can be used in condensation reactionsuch as MTBE or TAME processes in accordance with the present inventioncomprises an acidic zeolite in combination with a binder or matrixmaterial such as alumina, silica, or silica alumina. The preferredzeolites for use in the catalysts of the present process are the mediumpore size zeolites, especially those having the structure of ZSM-5,ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, MCM-22, mordenite,ferrierite, and zeolite L. The medium pore size zeolites are awell-recognized class of zeolites and can be characterized as having aConstraint Index of 1 to 12. Constraint Index is determined as describedin U.S. Pat. No. 4,016,218 incorporated herein by reference. Catalystsof this type are described in U.S. Pat. Nos. 4,827,069 and 4,992,067which are incorporated herein by reference and to which reference ismade for further details of such catalysts, zeolites and binder ormatrix materials.

The present process may also use catalysts based on large pore sizezeolites such as the synthetic faujasites, especially zeolite Y,preferably in the form of zeolite USY. Zeolite beta may also be used asthe zeolite component. Other materials of acidic functionality which maybe used in the catalyst include the materials identified as ZSM-20,MCM-36 (described in U.S. patent application Ser. No. 07/811,360, filed20 Dec., 1991) and MCM49 (described in U.S. Pat. No. 5,236,575). Theapplication and the patent describing MCM-36 and MCM-49, respectively,are incorporated herein by reference.

Thus, the preferred acidic zeolite catalysts are those exhibiting highalpha activity and having a zeolite structure of ZSM-5, ZSM-11, ZSM-12,ZSM-20, ZSM-22, ZSM-23, ZSM-35, ZSM-48, MCM22, MCM-36, MCM-49, zeoliteY, zeolite beta, mordenite, ferrierite and zeolite L.

The Alpha Test is described in U.S. Pat. No. 3,354,978, and the Journalof Catalysis, Vol. 4, pg. 527 (1965); Vol. 6, pg. 278 (1966); and Vol.61, pg. 395 (1980), each incorporated herein by reference as to thatdescription.

ZSM-5 crystalline structure is readily recognized by its x-raydiffraction pattern, which is described in U.S. Pat. No. 3,702,866.ZSM-11 is disclosed in U.S. Pat. No. 3,709,979, ZSM-12 is disclosed inU.S. Pat. No. 3,832,449, ZSM-22 is disclosed in U.S. Pat. No. 4,810,357,ZSM-23 is disclosed in U.S. Pat. Nos. 4,076,842 and 4,104,151, ZSM-35 isdisclosed in U.S. Pat. No. 4,016,245, ZSM-48 is disclosed in U.S. Pat.No. 4,375,573 and MCM-22 is disclosed in U.S. Pat. No. 4,954,325. TheU.S. Patents identified in this paragraph are incorporated herein byreference.

While suitable zeolites having a coordinated metal oxide to silica molarratio of 20:1 to 200:1 or higher may be used, it is advantageous toemploy aluminosilicate ZSM-5 having a silica:alumina molar ratio ofabout 25:1 to 70:1, suitably modified. A typical zeolite catalystcomponent having Bronsted acid sites may consist essentially ofcrystalline aluminosilicate having the structure of ZSM-5 zeolite with 5to 95 wt.% silica, clay and/or alumina binder.

These siliceous zeolites are employed in their acid forms, ion-exchangedor impregnated with one or more suitable metals, such as Ga, Pd, Zn, Ni,Co and/or other metals of Periodic Groups III to VIII. The zeolite mayinclude other components, generally one or more metals of group IB, IIB,IIIB, VA, VIA, or VIIIA of the Periodic Table (IUPAC).

Useful hydrogenation components include the noble metals of Group VIIIA,especially platinum, but other noble metals, such as palladium, gold,silver, rhenium or rhodium, may also be used. Base metal hydrogenationcomponents may also be used, especially nickel, cobalt, molybdenum,tungsten, copper or zinc.

The catalyst materials may include two or more catalytic componentswhich components may be present in admixture or combined in a unitarymultifunctional solid particle.

In addition to the preferred aluminosilicates, the gallosilicate,ferrosilicate and "silicalite" materials may be employed. ZSM-5 zeolitesare particularly useful in the process because of their regenerability,long life and stability under the extreme conditions of operation.

In the fixed bed embodiments of the present invention the catalyst mayconsist of a standard 70:1 aluminosilicate H-ZSM-5 extrudate having analpha value of at least 20, preferably 150 or higher.

Suitable pressure for the embodiments of FIGS. 1 to 7 range from aboutzero absolute to about 10,000 psig, preferably from about zero absoluteto about 2,000 psig, and more preferably from about zero absolute toabout 1,000 psig. Low pressure, specifically zero absolute pressure, issignificant because if one wants to use a condensation reaction with ahigh molecular weight material such as an octadecene (C₁₈) olefin anddimerize or condense it to C₃₆ olefin, either of VPR units of FIGS. 1 to7 would require working at very low pressure and preferable in a nearzero absolute range to vaporize the feed.

Conversely, if one was to condense a very low molecular weight feed suchas ethylene having an ambient vapor pressure of about 800 psig to anoligomer of a desired molecular weight, it would be necessary to operatethe VPR above 800 psig, and might well need to operate in excess 2000psig.

As discussed hereinabove, the pressure is tied to the temperature. Forexample, temperatures for MTBE and TAME reactions are in the range offrom about 120° F. to about 400° F., and preferably from about 140° F.to about 180° F. Pressure is proportional to temperature, and inverselyproportional to reactant molecular weight. Specifically, low molecularweight reactants and high reaction temperature require high or highestpressures. Conversely, high molecular weight reactants and low reactiontemperatures call for lower or lowest pressures. Although the disclosedembodiments couple pressure and temperature, decoupling the pressure andtemperature is also contemplated by this invention.

The preferred WHSV for the TAME and MTBE processes ranges from about 0.1to about 10.0 hr⁻¹, and preferably from about 0.5 to about 2.0 hr⁻¹.

As used herein "bulk separation" means separation of a batch orcontinuous feedstream by a catalytic reaction process into multipleoutput or product steams such as occurs in prior art catstills, in atypical autoclave batch reactor and in the above described FIG. 5embodiment. Although the embodiments of FIGS. 1 to 4 and 7 have internalflow or stream separations, each system processes a single feedstreaminto a single output or product steam, and therefore does not provideseparation.

While the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace all such alternatives, modification, and variations as fallwithin the spirit and broad scope of the appended claims.

What is claimed is:
 1. A reaction process for converting in a closedreactor at least one reactant to at least one reaction product having avapor pressure less than the vapor pressure of each of said at least onereactant, said process comprising the steps of:heating in said reactor aliquid phase comprising said at least one reactant to partialvaporization thus forming a vapor phase of said at least one reactant;passing said at least one reactant of said vapor phase in a vapor and/orcondensed state through at least one catalyst bed spaced in said reactorfrom said liquid phase for converting said at least one reactant of saidvapor phase to said at least one reaction product; and returning said atleast one reaction product from said at least one catalyst bed to saidliquid phase without additional contact with catalyst.
 2. The process ofclaim 1 further comprising continuing reflux of said at least onereactant between said liquid phase and said vapor phase until a desiredconcentration of said at least one product is in said liquid phase. 3.The process of claim 1 wherein said at least one reactant of said vaporphase is condensed to liquid prior to contacting said at least onecatalyst bed.
 4. The process of claim 1 wherein said vapor phase of saidat least one reactant passes through said at least one catalyst bed, andsaid at least one reaction product is condensed prior to being returnedto said liquid phase.
 5. The process of claim 1 wherein said process isa reversible catalytic etherification process for converting volatileisoalkene and alkanol reactants, and wherein said at least one reactionproduct is an ether product.
 6. The process of claim 5 wherein saidisoalkene comprises isobutene, said alkanol comprises methanol, and saidether product comprises methyl tertiary butyl ether.
 7. The process ofclaim 5 wherein said isoalkene comprises isoamylene, said alkanolcomprises methanol, and said ether product comprises tertiary amylmethyl ether.
 8. The process of claim 1 wherein said process is a MTBEor TAME process, and wherein said at least one catalyst bed includescation exchange resins which contain sulfonic acid groups obtained bypolymerization or copolymerization of aromatic vinyl compounds followedby sulfonation.
 9. The process of claim 1 wherein said process is a MTBEor TAME process, and wherein said at least one catalyst bed comprises H₃PO₄ on Kieselguhr, AlCl₃, ZrO₂ -H₂ S0₄, BF₃ -Si0₂, AlCl₂ /Si0₂, MgO₂(base), Nafion-4, or combimations thereof.
 10. The process of claim 2wherein said process is a MTBE or TAME process, and wherein said atleast one catalyst bed includes ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23,ZSM-35, ZSM-48, MCM-22, mordenite, ferrierite, or combinations thereof.11. The process of claim 1 wherein said process is a MTBE or TAMEprocess, and wherein said at least one catalyst bed includes zeolite Y,beta, ZSM-20, MCM-36, MCM-49, or combinations thereof.
 12. The processof claim 1 wherein said liquid phase comprises methanol and olefins in amole ratio of about 1:1, and wherein said vapor phase comprises methanoland olefins in a mole ratio of from about 3:1 to about 4:1.
 13. Theprocess of claim 1 wherein said vapor phase has a methanol to olefinsmole ratio greater than that of the reactants.
 14. The process of claim1 wherein pressure at said catalyst bed is proportional to desiredreaction temperature and inversely proportional to the molecular weightof the reactants.
 15. The process of claim 1 wherein a quantity saidliquid phase of reactants is placed in a bottom portion of a closedvessel, a catalyst bed is spaced above said reactants and a condenser ispositioned above said catalyst bed, and wherein said vapor phase passesupwardly around said catalyst bed to said condenser, said condensertransforming said vapor phase reactants to condensate, said condensatepassing through said catalyst, bed for producing said reaction product,and said reaction product exiting said catalyst bed and falling to saidliquid phase, said heating step being continued to reflux the reactantsbetween said liquid phase and said vapor phase until a desiredconcentration of said product is in said liquid phase.
 16. A reactor forconverting at least one reactant to at least one reaction product havinga vapor pressure less than the vapor pressure of said at least onereactant comprising:means for heating a liquid phase comprising said atleast one reactant to partial vaporization thus forming a vapor phase ofsaid at least one reactant; means including at least one catalyst bedspaced from said liquid phase for converting the at least one reactantof said vapor phase to said at least one reaction product; means forpassing the at least one reactant of said vapor phase in a vapor and/orcondensed state through said at least one catalyst bed; and means forreturning said at least one product to said liquid phase withoutadditional contact with catalyst.
 17. The reactor of claim 16 furthercomprising means for controlling reflux of reactants between said liquidphase and said vapor phase until a desired concentration of said atleast one product is in said liquid phase.
 18. The reactor of claim 16wherein each of said catalyst beds is supported by a foraminoushorizontal support.
 19. The reactor of claim 16 wherein each of said atleast one catalyst bed is supported by a screen structure.
 20. Thereactor of claim 16 wherein each of said at least one catalyst bed isformed of an array of permeable plates.
 21. The reactor of claim 16wherein said converting means comprises a plurality of condensationtrays vertically spaced in said reactor, and one of the catalyst bedssuspended beneath each one of said trays.
 22. The reactor of claim 21wherein said passing means comprises one-way means on each one of traysfor permitting flow of said vapor phase upwardly from the catalyst bedtherebelow and for preventing liquid flow downwardly from the tray tothe catalyst bed.
 23. The reactor of claim 22 wherein said returningmeans comprises means serially connecting said trays for providing aliquid path from the top tray to the bottom tray without contacting thecatalyst beds.
 24. The reactor of claim 16 wherein said passing meanscomprises a source of makeup feed, a makeup feed preheater connected tosaid source, a conduit interconnecting said preheater and a location insaid reactor between said catalyst bed and said liquid phase, and meansinterconnecting said preheater and said reactor above said catalyst bedfor maintaining a positive pressure on the upper portion of saidcatalyst bed,whereby said positive pressure means forms a loop byforcing vapor into said conduit, through said preheater where a minorportion of makeup feed is admixed therewith, into said reactor,downwardly through said catalyst bed for conversion to said at least oneproduct, said product condenses and falls into said liquid phase, andsaid vapor returns to said conduit.
 25. The reactor of claim 16 whichincludes a liquid phase comprising reactants in a bottom portion of thereactor, a catalyst bed spaced above said bottom portion of said reactorcontaining said liquid phase, a tray above said catalyst bed, an openingis formed in said tray to said catalyst bed, a pump for pumping liquidthrough said opening in said tray to said catalyst bed, a condenserpositioned above said tray, and a source of fresh feed above saidcondenser, and wherein said vapor phase passes upwardly around saidcatalyst bed to said condenser, said condenser transforming said vaporphase reactants to condensate, said condensate passing through saidcatalyst bed for producing said reaction product, and said reactionproduct existing said catalyst bed and falling to said liquid phase. 26.The reactor of claim 16 wherein said passing means comprises a source ofmakeup feed, a makeup feed preheater connected to said source, a conduitinterconnecting said preheater and said reactor above and said liquidphase, said catalyst bed being located in said conduit, and meansinterconnecting said preheater and the upper portion of said reactor formaintaining a positive pressure therein,whereby said positive pressuremeans forms a loop by forcing vapor into said conduit, through saidcatalyst bed for conversion to said at least one product, into saidpreheater where a minor portion of makeup feed is admixed with said atleast one product, into said reactor, wherein said product condenses andfalls into said liquid phase, and said vapor returns to said conduit.